The invention set forth in this specification pertains to a new and improved combination of an indicator and a pneumatically operated machine. More precisely it pertains to indicators used with such machines to provide a signal or indication (1) only when such a machine is operated in the reverse of the normal manner in which it is operated, (2) is not being operated or (3) when such a machine is either being operated in such a reverse manner or is not being operated at all.
Virtually everyone is familiar with the fact that indicators capable of producing an audible signal are often used with various items of equipment in order to provide a warning when such items of equipment are operated in the reverse of the manner in which they are normally operated. Thus, various types of trucks and other vehicles are frequently provided with a bell type mechanism which is actuated when such a vehicle is operated in reverse. The use of such an indicator is often quite desirable in order to minimize the possibility of an accident occurring.
Normally such indicators or indicator mechanisms as noted are comparatively complex and/or complicated type devices involving more than a very few comparitively simple parts. Since the cost of a comparatively complex indicator is usually quite minor as compared to the cost of a large item of equipment such as, for example, a truck, a bus or a vehicle especially constructed to serve a specialized construction purpose the cost of an indicator normally is not a significant deterrent to the use of an indicator with such vehicles and various other related machines.
However, this is not the case when it is desired to use an indicator to provide an audible signal to indicate that a comparatively small or simple, relatively inexpensive machine is being operated in other than a normal manner, has been stopped or is either not being operated at all or is not being operated in such a manner. Such a simple machine can be defined as a mechanical system of mechanical parts which are connected together so as alter, transmit and direct an applied force in a predetermined manner in order to accomplish a specific objective. Normally the objective is useful work. Frequently conventional indicators for providing an audible signal as discussed in the preceding are or can be nearly or more expensive than a comparatively simple machine.
In cases such as this there is a tendency not to use an audible indicator because of the cost of the indicator as compared to the cost of the machine. While often times there is no significant need to use an audible indicator with a machine on other occasions there is often a real need to use such an indicator with a simple or comparatively simple machine. Usually this need is particularly pronounced in a case where there there is a distinct possibility of damage or harm resulting from a machine being operated in the reverse of the normal manner in which it is operated.
These factors can be illustrated in connection with a presently preferred application of the invention in the field of dental drills or drilling machines. Frequently these are comparatively simple pneumatic devices which use compressed air from a source of the latter to drive a simple air motor which is coupled to or holds a drill bit. As a result of factors which are unimportant to the present invention if bits such as are used in the placement of artificial tooth roots or bodies are rotated in reverse there can be a significant danger of damage to the mouth of a dental patient.
If an indicator was used with such a drilling machine a dentist in using the drill would be immediately aware of the fact that the drilling machine was being operated in reverse if for any reason the machine should be operated in such a reverse manner. As a result of this a dentist would be able to take remedial action so as to avoid damage or any further damage before any significant harm was done if a drill should be operated in other than an intended or normal manner.
Unfortunately it is considered that audible indicators indicating a reverse or other than intended manner of operation of dental drilling machines have not normally been used or have not been used at all in the past. Although the precise reason or reasons for this are not known it considered that cost has been a material factor in preventing the use of audible indicators to provide an indication when a drill or drilling machine is not being operated in a normal or "forward" manner.